The invention relates to an assembled shaft comprising a tubular member and driving or coupling elements attached to it, especially a camshaft or driveshaft, as well as a process for producing such a shaft. Camshafts and driveshafts are only given by way of example, other applications also being possible.
Camshafts produced in accordance with the above mentioned process have already been described (P 36 33 435.9). Like conventional single-part shafts, camshafts of this type are guided in friction bearings whose size is determined by the diameter of the shaft member whose cross section is determined by existing strength requirements. It goes without saying that with the same boundary conditions, i.e. especially with a pre-determined torque load, the outer diameters of shafts with a hollow tube member are usually larger than those of solid shafts. Apart from the strength of the tube itself, it is especially the seat surface required for a friction-locking fit of the driving or coupling elements on the tubular member which is decisive. A further aspect in determining the size of the tubular member is the required inner diameter which must be free for inserting a probe for connecting the tubular member and the driving elements.
A disadvantage of the above mentioned shafts is that, because of the size of their bearings, they have an undesirably high friction loss. Furthermore, the problem of bearing lubrication is not solved satisfactorily because for supplying the lubricating oil special measures have to be taken inside the shaft which increase production costs.